The long-range goal of this research proposal is to understand the assembly and dynamics of an essential eukarydtic organelle, the mitochondrion. The assembly of mitochondria is dependent upon the import of proteins from the cytosol, a process that utilizes complicated machinery in both the mitochondrial inner and outer membranes. Although much of the import apparatus has been identified, additional import components await identification. In addition, many unanswered question remain about the mechanism by which preproteins are translocated across the mitochondrial membranes, or inserted into the hydrophobic environment of the lipid bilayer. [unreadable] [unreadable] Mitochondria are also dynamic organelles, continuously fusing, dividing and moving within cells by processes under exquisite control. Mitochondria also show a wide variety of shapes and numbers in different cell types. Although the dynamic nature of mitochondria has been documented for over TOO years, little is known about the molecules or mechanisms mediating the fusion, division, segregation and shape of the organelle. [unreadable] [unreadable] To further our understanding of mitochondrial assembly and dynamics, we have isolated mutants in the yeast, Saccharomyces cerevisiae, that are defective in mitochondrial function. We propose to continue our analyses of mitochondrial proteins identified by our genetic stusies, and will focus on the following questions: [unreadable] [unreadable] 1) How is mitochondrial shape established and mtDNA maintained? [unreadable] 2) What is the mechanism of mitochondrial protein import, and how is it related tomitochondrial shape? [unreadable] 3) What is the mechanism of mitochondrial division? [unreadable] 4) What is the mechanism of mitochondrial fusion? [unreadable] [unreadable]